1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a printing method for forming black matrixes in a liquid crystal display device.
2. Description of the Related Art
Demands for a light, thin, small flat panel display devices is increasing due to the development of various portable electronic devices, such as mobile phones, PDAs, notebook computers, and the like. As a result, there has been an increase in research with regard to flat panel display devices including an LCD (Liquid Crystal Display), a PDP (Plasma Display Panel), an FED (Field Emission Display), a VFD (Vacuum Fluorescent Display) and the like. Liquid crystal display devices are receiving much attention thanks to its simple mass-production technique, easy driving system and implementation of a high picture quality.
FIG. 1 is a schematic view illustrating a section of a general liquid crystal display device. As illustrated in FIG. 1, a liquid crystal display device 1 includes a lower substrate 5, an upper substrate 3 and a liquid crystal layer 7 formed between the lower substrate 5 and the upper substrate 3. A pixel electrode and a common electrode (not shown) are respectively formed on the lower substrate 5 and the upper substrate 3, and an alignment layer (not shown) for aligning liquid crystal molecules of the liquid crystal layer 7 is formed on the pixel electrode and on the common electrode.
The lower substrate 5 is a driving unit array substrate including a plurality of pixels (not shown). Each pixel includes a driving unit such as a thin film transistor. The upper substrate 3 is a color filter substrate including a color filter layer for implementing a color.
The lower substrate 5 and the upper substrate 3 are attached by a sealing material 9, and the liquid crystal layer 7 is formed there between. The liquid crystal molecules of the liquid crystal layer are driven by a driving unit (not shown) formed on the lower substrate 5 and the quantity of light transmitting the liquid crystal layer is controlled to display information.
The lower substrate 5 is formed by a driving device array process for forming the driving device at the lower substrate 5, and the upper substrate 3 is formed by a color filter process for forming a color filter.
The driving device array process includes forming a plurality of gate lines and data lines which are arranged on the lower substrate 5 and define pixel regions, forming at each pixel region a thin film transistor which is the driving device to be connected to the gate lines and data lines, and then forming a pixel electrode for driving the liquid crystal layer by applying a signal through the thin film transistor which is connected thereto (to the pixel electrode).
Furthermore, the color filter process is achieved by forming black matrixes on the upper substrate 3, forming a color filter on the black matrixes, and forming a common electrode on the color filter. The black matrixes are formed using a single layer of metal material having excellent reflective properties such as Cr or CrOx, or a double layer which shields light more effectively. However, the double layer black matrixes requires a photolithographic process. In general, black matrixes made of a metal pattern are fabricated using a photolithographic process, which includes complicated processes such as metal film deposition, exposure, development, and strip processes. As a result, the addition of the photolithographic process decreases productivity.
Alternatively, the black matrixes may be made of a resin BM. The black matrix resin is thicker than the metal layer in order to effectively block light. That is, because the resin BM uses a spin coater, it has a limit to reduce a thickness. However, as the resin BM becomes thicker, an occurrence of step difference is deepened. In order to solve the problem, an overcoat layer has to be formed, or after forming the resin BM, a polishing process for eliminating its surface has to be applied thereto.
Thus, in both related art black matrix forming processes productivity is reduced due to the required additional process. For example, when employing the double metal layer, the photolithographic process is further required, and when employing the resin BM, the overcoat layer forming or polishing process is further required.